1. Field of the Invention
The present invention relates to novel polyether polyurethanes which form tough gels, soft elastic gels, high slip materials and solutions specifically adapted for use in burn and wound care dressings, plastic surgery implants, heat and cold-retentive applications, pressure absorbing applications, electroconductive surgical pads, drug delivery systems, antiperspirants, tubing and molded devices, medical, cosmetic and industrial applications.
2. Description of the Related Art
U.S. Pat. No. 4,810,582 of a common ownership to the present invention describes blends of hydrophilic polyurethanes derived from blending a polyoxyalkylene glycol with a polyester polyurethane. The polyester polyurethane is the reaction product of an aromatic diisocyanate and a polyol. The polymer blend absorbs water when immersed in water and retains its mechanical strength. A film formed from the polymer blend can be used in a burn dressing. The film can contain a medicament, hormone or a steroid. The polymer blend can be extruded and molded. For example, the polymer blend can be used in a diaphragm, cannula, contact lens, corneal prosthesis and dialysis membrane.
U.S. Pat. No. 5,000,955 of common ownership with the present invention relates to thermally reversible polyurethane hydrogels. This patent describes that when polyether polyurethanes are formed under anhydrous conditions they form hydrogels in water. The hydrogels are solids at room temperature but liquefy at higher temperatures, such as body temperature. The hydrogels can be used for, controlled delivery and sustained release of an active agent. The active agent is encapsulated in the gel matrix for immobilizing and protecting the agent. On lowering the viscosity of the hydrogel by raising the temperature, the active material becomes mobile. The active material can include drugs, cosmetic additives, salts, and food additives. The hydrogels can also be used as nontoxic culture media for the growth of microorganisms. In addition, the polymer forms a solution at 25% solids in ethanol having a viscosity of 1200 cps which can be used for the preparation of face masks and dry-skin protectants.
U.S. Pat. Nos. 3,822,238 ('238 patent) and 3,975,350 ('350 patent) describe a class of hydrophilic polyurethane polymers which absorb water with the concomitant formation of a stable, water-insoluble hydrogel. The '350 patent describes that when the cross-linked polymers are in the wet state they range from gel-like polymers to polymers being compliant, soft and flexible. Alternatively, about 0.01 to about 0.6% of a polypropylene polyol, preferably 0.05 to 0.5% , more preferably from 0.06 to 0.4%, with a molecular weight of about 100 to about 7000 can be added. The hydrogels can be used in various applications such as in coatings, linings, membranes, absorbent, swellable fabrics, gauzes and the like. The hydrogels can be cured to form solid or shaped bodies, such as rod sheets and tubes. However, the '238 and the '350 patents have the shortcomings of not being soluble in dilute glycol/water solutions, not forming jelly-like gels at moderate concentrations, of retaining their shape in water, and not becoming flowable at high temperatures, making them capable of being extruded into forms and not having sufficient mechanical strength to be tough at body temperature which property is preferable for certain applications. The '350 patent teaches a polymer that precipitates out of a methanol solution upon the addition of water and the polymer is cross-linked.
U.S. Pat. No. 5,273,742, of common ownership to the present invention describes a method for replacing ocular fluid in an eye and for replacing intra-articular fluid in a joint by introducing an aqueous solution of a water soluble hydrogel in an amount of 0.5% to 7% weight of polymer. In both applications, the polymer forms an injectable solution of the water-soluble hydrogel. However, the water-soluble hydrogel does not form a tough gel at body temperatures.
U.S. Pat. No. 5,120,816 of common ownership to the present invention describes a polyurethane resin having improved tear strength in which the amount of water in the reaction mixture is claimed to be in the range of about 1.0% to about 2.5% weight percent. The use of a large amount of water provides insoluble polymers which have high strength in water. However, this type of polyurethane resin does not form tough gels.